Rainey was born in Lakeland, Florida, the son of a single mother, and was raised, in part, by his grandmother.[1] He attended Lakeland High School, where he became a standout running back for the Lakeland Dreadnaughts high school football team.[2] During his high school years, he lived with the family of twin brothers Maurkice Pouncey and Mike Pouncey, and all three were standout members of the Dreadnaughts football team.[1] As a senior in 2006, he led his team with 2,478 yards rushing for thirty-two touchdowns—including fifteen touchdown runs of fifty yards or more—and helped lead the Lakeland Dreadnaughts to their third consecutive Florida Class 5A state championship and second straight USA Todaynational championship.[2] Following his senior season, he was a U.S. Army high school All-American and an all-state selection by the Florida Sports Writers Association, and finished his prep career with more than 7,000 all-purpose yards and ninety touchdowns.[2]

Rainey and the Pouncey brothers all committed to play college football for the University of Florida. All three would later be drafted by NFL teams.

Rainey accepted an athletic scholarship to attend the University of Florida in Gainesville, Florida, where he played for coach Urban Meyer and coach Will Muschamp's Florida Gators football teams from 2007 to 2011.[3] After injuring his shoulder as a true freshman in 2007, he was redshirted.[2] He was a member of the Gators' 2008 team that won the 2008 SEC Championship Game and the 2009 BCS National Championship Game.[2] During his career as a Gator, he played in fifty-two games, compiled 2,464 yards and thirteen touchdowns on 396 rushing attempts, 795 yards and six touchdowns on sixty-nine receptions, and 454 return yards on eighteen kickoffs.[2] On special teams, he holds the team career record for blocked kicks (4).[3] Following his senior season in 2011, his fellow Gators recognized him as the team's most valuable player.

As a freshman, he also ran the 100-meter dash for the Florida Gators track and field team, and received All-American honors as a member of the Gators men's third-place 4x100-meter relay team at the 2008 NCAA national outdoor track and field championships.[4]

Rainey did not participate in track as a sophomore. As a junior in 2010, the Gators men's 4x100-meter relay team, including Rainey, Jeremy Hall, Terrell Wilks and Jeff Demps, won the NCAA championship in the event with a winning time of 39.04 seconds.[5] The quartet received All-American honors for their first-place finish.

The Pittsburgh Steelers selected Rainey in the fifth round, 159th overall pick, of the 2012 NFL Draft,[7][8] and the team announced he had signed a four-year contract on May 6, 2012.[9][10] He debuted for the Steelers against the Denver Broncos on September 9, 2012 and scored his first NFL touchdown against the Cincinnati Bengals October 21, 2012.

The Steelers waived Rainey on January 10, 2013, after he was arrested on a battery charge.[11]

Rainey signed with the Indianapolis Colts on November 20, 2013.[12] Chris spent three weeks with Indianapolis. His first week, given limited practice time with the team, he was inactive. Rainey would, however, appear in the next two contests for the Colts; Weeks 13 & 14. Immediately following their Week 14 match-up, a losing effort to the Cincinnati Bengals, Indianapolis announced Monday December 9, that Rainey had been placed on season-ending Injured Reserve. In his two games with the Colts Rainey returned six kickoffs and four punts for a total of 160 all-purpose yards. Despite being used in a few third-down packages Rainey failed to make any offense contributions in his very limited time with Indianapolis.[13] On July 28, 2014 Colts coach Chuck Pagano announced Chris Rainey had been released from the team citing, "It's unfortunate and [a] violation of team rules. It was an in-house deal, that's all I'm going to say about that."[14][15]

Rainey was arrested January 10, 2013 and charged with one count of simple battery against his girlfriend by the Gainesville police. Soon after the arrest, Rainey was waived by the Pittsburgh Steelers.[17] Soon after the Steelers released him, the charges were dropped.

Rainey's older brother is former XFL and NFL running back and kick returner Rod Smart.[18]